When a taddhita affix having an indicatory ñ , ṇ or k follows, ā is substituted instead of vṛddhi for the first vowels of the following - 1. devikā 2. śiṃśapā 3. dityavāṭ 4. dīrghasatra and 5. śreyasa,
Thus दाविकम् (= देविकायां भवम्) in दाविकमुदकम्; दाविकाकूलाः शालयः (= देविकाकूले भवाः), पूर्वदाविकः from पूर्वदेविका 'the name of a village of the Eastern people'. Here the vriddhi of the second member ordained by 7.3.14, becomes आ ॥ Similarly शांशपचमसः (= शिंशपायाविकारः) ॥ The word belongs to the Palasadi class 4.3.141, and takes अण् or अञ्, the difference being in accent. So also शांशपास्थलाः (= शिंशपास्थले भवाः), and पूर्वशांशप from पूर्वशिंशपः 'the name of a village' See 7.3.14. Similarly दात्यौहम् from दित्यवाह्, (दित्यौह इदं) and दार्घसत्रम् (दार्घसत्रे भवं) and श्रायसम् (श्रेयसि भवं) ॥
Vart:- The Vriddhi of वहीनर under similar circumstances is with an ऐ as if व was वि, as वहीनरस्यापत्यं = वैहीनरिः ॥ Some say the original word itself is विहीनर (विहीनोनरः), and so its taddhita derivative is regular.,